Sams "PoolBrand" dichlor and trichlor is fine.

The Costco products we've seen locally (Chattanooga) are blended goop. But, this trichlor is fine:
http://www.costco.com/Browse/Product...rodid=11617928
though THIS trichlor powder is a mess:
http://www.costco.com/Browse/Product...rodid=11524614